Sexual size dimorphism (SSD) is often assumed to reflect the phenotypic consequences of differential selection operating on each sex. Species that exhibit SSD may also show intersexual differences in other traits, including field‐active body temperatures, preferred temperatures, and locomotor performance. For these traits, differences may be correlated with differences in body size or reflect sex‐specific trait optima. Male and female Yarrow's spiny lizards,
- NSF-PAR ID:
- 10321069
- Date Published:
- Journal Name:
- Journal of Experimental Biology
- Volume:
- 225
- Issue:
- Suppl_1
- ISSN:
- 0022-0949
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Sceloporus jarrovii , in a population in southeastern Arizona exhibit a difference in body temperature that is unrelated to variation in body size. The observed sexual variation in body temperature may reflect divergence in thermal physiology between the sexes. To test this hypothesis, we measured the preferred body temperatures of male and female lizards when recently fed and fasted. We also estimated the thermal sensitivity of stamina at seven body temperatures. Variation in these traits provided an opportunity to determine whether body size or sex‐specific variation unrelated to size shaped their thermal physiology. Female lizards, but not males, preferred a lower body temperature when fasted, and this pattern was unrelated to body size. Larger individuals exhibited greater stamina, but we detected no significant effect of sex on the shape or height of the thermal performance curves. The thermal preference of males and females in a thermal gradient exceeded the optimal temperature for performance in both sexes. Our findings suggest that differences in thermal physiology are both sex‐ and size‐based and that peak performance at low body temperatures may be adaptive given the reproductive cycles of this viviparous species. We consider the implications of our findings for the persistence ofS. jarrovii and other montane ectotherms in the face of climate warming. -
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Abstract Aim High heat tolerance is a potential way for plants to maintain performance under high temperatures that can be acted upon by environmental filters to influence community assembly. Plant heat tolerances are phenotypically plastic and thus common garden experiments are needed to test if species from hotter environments have consistently higher heat tolerance than species from colder environments. Past studies that have measured heat tolerance from species grown in common gardens have found conflicting relationships between species' climatic origins and their heat tolerance, possibly due to phylogenetic non‐independence of study species. In this study, we test the hypothesis that phylogenetic structure can help to explain variation in heat tolerance in order to resolve the confliciting relationships between climate and plant heat tolerance.
Location Fairchild Tropical Botanic Garden and the Gifford Arboretum, Miami, FL, USA.
Taxon Pteridophytes, Gymnosperms and Angiosperms.
Methods We tested for phylogenetic signal in the photosynthetic heat tolerance of 123 species of ferns, gymnosperms, magnoliids, monocots and eudicots by calculating Blomberg's K. Phylogenetic independent contrasts of heat tolerance and climatic distributions for >100 species were used to test the hypothesis that climate can predict variation in heat tolerance.
Results Species' heat tolerances were not phylogenetically conserved according to Blomberg's K, but we found significant differences in the heat tolerance of ferns, gymnosperms, magnoliids, monocots and eudicots. When controlling for phylogenetic non‐independence, we found a significant, but weak relationship between the mean maximum temperature of the warmest month of species' climatic distributions and their photosynthetic heat tolerance.
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1242/jeb.243292
